As you dig into your Thanksgiving leftovers this weekend, could the tryptophan in your favorite holiday dishes render you less likely to make those regrettable impulse purchases when you head out to do your holiday shopping?

This was the hypothesis put forward by Arul Mishra and Himanshu Mishra, who noted in a recent study that serotonin, a neurotransmitter with strong links to lower impulsivity, lower aggression, and higher levels of cooperation, is actually synthesized from tryptophan -- meaning that consuming a higher-than-average amount of tryptophan (as we often do on Thanksgiving) might render people less likely to buy things on impulse.

In their first study, 170 people were asked on Thanksgiving evening if they would be willing to purchase a fancy new Dell computer, deeply discounted with free shipping and a free printer if they ordered ASAP. Of the 170 people, 113 of them had consumed a "traditional" Thanksgiving dinner including turkey and lots of carbs -- all ideal for producing high amounts of serotonin. The other 57 had eaten "non-traditional" dinners, like pizza, burritos, salmon, or noodles. Although the two groups didn't differ in their reported moods (meaning the Thanksgiving Dinner folks weren't any happier or more relaxed), those who had eaten a typical Thanksgiving dinner were less likely to say they would buy the computer. This difference between the two dinner groups was especially pronounced when comparing naturally impulsive people in each one.

The researchers later replicated this finding in a smaller laboratory study; participants who consumed a tryptophan-enhanced protein shake performed better on a Go-No Go task (a game designed to measure impulsivity where you have to push a button only when certain numbers pop up on the screen, but not others) and were more likely to say that they would purchase a TV using layway financing rather than purchasing it on credit (the less "instant gratification"-friendly one of the two options).

Overall, participants who consumed tryptophan -- an amino acid present in many of our favorite Thanksgiving staples, which is metabolized in our bodies into the neurotransmitter serotonin -- were less impulsive, less aggressive, and less inclined to make "impulse buys" when shopping.

But This Doesn't Seem Like Black Friday

Carbs and turkey may render us less likely to behave aggressively, act on impulse, or make regrettable spur-of-the-moment consumption choices? This doesn't seem like the post-Thanksgiving Black Friday that we all know.

Well, we already know from past research that consumer behavior can be swayed by many different things, including background music, brand exposure, and others' salient behavior. Despite this one finding, Black Friday also has a lot of other really strong contextual factors working in its favor to make it the maelstrom we know it to be.

For example, perceptions of scarcity have a very strong impact on our purchasing behavior. Perceiving a certain good to be scarce (either because it's available for a "limited time only" or because of excessive demand from other buyers) leads people to assume that the product must be high-quality, highly desirable, and unique -- making it more likely that they will leap on opportunities to purchase the product. Shoppers facing a time pressure -- like, say, a deal only available for a certain period of time -- are also morelikely to make impulsive purchases. Finally, deindividuation -- the sensation of feeling anonymous and less self-conscious in a group -- is associated with more impulsive, aggressive behavior, and it is specifically cultivated by large, loud, energized groups -- exactly the kind that might be present at a "door-buster" Black Friday sale.

Your Thanksgiving leftovers may leave you full of food and serotonin -- a neurotransmitter that can lower impulsive behavior. But, don't get too excited about your binge-induced willpower. Black Friday has a lot of stuff going on to pull you in the other direction, too.

ABOUT THE AUTHOR(S)

Melanie Tannenbaum

Melanie Tannenbaum is a freelance writer and science communications consultant currently living in the Bay Area. She received her Ph.D. in social psychology from the University of Illinois at Urbana-Champaign in 2015, where her research focused on the science of persuasion and motivation regarding political, environmental, and health-related behavior. For more info, see her personal website.

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